with 400 AP fiddle would have 490 dps crowstorm to rammus's 315 (56% more dmg)
BUT total dmg(dps*duration) = 2450____________<_____________2520

of course fiddle will probably get much more AP than that but see these next stats:

rammus can ult 2.50 times per crowstorm
or_____________3.33 times per crowstorm (with frozen heart)

so rammus has less "burst" in his ult, also no 800 range teleport surprise, BUT
he can powerball around while ulting and hes way more survivable than squishy fiddle,
who often gets whacked before he finishes ulting or even before he can finish the
2 second channel to teleport